airborne(transmission(and(precau1on(–facts(and(myths( prof ... · airborne precaution airborne...

Airborne Transmission and Precau1on – Facts and Myths Prof. W.H. Seto, Hong Kong

Broadcast live from the 2014 Healthcare Infec1on Society conference, Lyon, France

A Webber Training Teleclass www.webbertraining.com

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WH Seto, HK, China

Airborne transmission and precaution – facts and myths

www.webbertraining.com November 17, 2014

Edward Joseph Lister Lowbury (1913 - 2007)

A pioneering and innova/ve English medical bacteriologist and pathologist and also a

published poet.

Acknowledgements:

Prof. Ben Cowling, School of Public Health, University of Hong Kong

Prof. Yugio Li, Dept. of Mechanical Engineering, University of Hong Kong

Bacteria That Cause Airborne Nosocomial Infections

• Group A Streptococcus • Staph. aureus • Neisseria meningitidis • Bordetella pertusis • MTB

Viruses Implicated in Airborne Nosocomial Infections • Rinoviruses • Influenza and • Parainfluenza viruses • Respiratory Syncytial Virus • Adenovirus




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aerosol

Normal alveolar

Pneumonia

Courtesy: Dr Gavin Chan, Department of Pathology

Queen Mary Hospital

Recent classification for airborne transmission

Obligate airborne: initiate solely through aerosols: TB

Preferential airborne: initiate through multiple routes but predominately by aerosols: Chicken pox and measles

Opportunistic airborne: typically through other routes but by aerosols in favorable conditions (as high-risk procedures such as intubation): Influenza and SARS

2014 WHO ARI Guideline




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Transmission Based Precaution

Isolation Room Single room - Negative Pressure Keep doors closed

N95

Airborne Precaution

Airborne infection isolation room (AII):

• Single room or cohorting • Negative pressure (-2.5 Pa) • 12 air changes per hour for new renovations • Exhaust air outside or recirculated by HEPA filters

A tightly sealed respirator blocked 99.8% of total virus and 99.6% of infectious virus (n = 3). A tightly fitted (surgical) mask block 94.5% of the total virus and 94.8% of the total infectious virus.

Noti JD, Lindsley WG, Blachere FM. et al: Detection of influenza virus in cough aerosol generated in a simulated patient examination room. Clin Infect Dis 2012; 54 (1 June) 1569-1577

General consensus on the N95 Respirator to prevent airborne transmission

A. Are Most Respiratory Viral Infections Airborne?

Most studies done – Influenza and SARS




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Is Influenza Airborne? Reviews Clinical Trials Comparing N95 and Medical Masks

New Experimental Studies

Two major reviews

Transmission of influenza A in human beings

Brankston et al. Lancet ID 2007(7):257-65

Search of 2012 citations

More a systemic review

Artificial generated aerosol can infect man and animals

Artificial aerosols: <10% are larger 8 µm Natural coughing: 99.9% are larger then 8 µm

“We question whether these studies are relevant to natural route of human transmission”

“No published evidence of human infection resulting from the ambient air”

Alaskan Airline: Non functional ventilation system 72% infected (Am J Epidemiol 1979:110:1-6) Free movement of passengers

Naval base aircraft (Am J Epidemiol 1989:129:341-48) Klontz reported outbreaks (56%) in functional ventilation planes

Influenza lower with UV lights in VA hospital (Am Rev Resp Dis 1961:83:36) Infection related to ventilation systems in 4 buildings (J Am Ger 1996:18:811)

• Many confounders not accounted: eg. number of index patients, bed layout, length of stay, hand hygiene, immunization status. One study even confirmed that lowest rate has more space allocated

• Air exchange rate is not reported • 2nd study even reported equal rates in next season.

Clinical Trials Comparing N95 and Medical Masks.




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http://www.who.int/csr/resources/publications/cp150_2009_1612_ipc_interim_guidance_h1n1.pdf

This guidance replaces guidance documents issued on 29 April and 25 June 2009 and remains valid until 30 June 2010,

III, 1.1 - Standard & Droplet Precautions should always be applied

III,1.2 - performing aerosol-generating procedures wear a particulate respirator

III, 4. Collection of laboratory specimens Upper respiratory tract (above larynx) Standard and Droplet Precaution Lower respiratory tract specimens Aerosol-generating procedures IPC measures

WHO guidance for infection prevention and control for H1N1

“At the start of the 2009 outbreak, there was uncertainty

regarding the transmission dynamics of the novel H1N1

virus. While seasonal influenza is spread by large

respiratory droplets, a concern at the onset of any

potential influenza pandemic is whether the pathogen

will have a different dynamics or methods of spread.”

13th May – CDC recommends N95 to be used in all situations

Recommendation for 2009 H1N1 Pandemic

Surgical Mask vs N95 Respirator for Preventing Influenza Among Health Care Workers: A

Randomized Trail. Mark Loeb et al, JAMA,, 2009;302(17), October 1 online

A randomized controlled trail of 446 nurses in 8 tertiary care hospitals – Ontario

Surgical masks N95 n = 225 221 Influenza infected = 50 (23.6%) 48 (22.9%)

p = 0.086 (meet criteria for non-inferiority)

But there is a study not considered by IOM showing that surgical masks is as effective as N95…………. HICPIC advisory committee

23rd July 2009 to vote on the latest recommendation (http://www.cdc.gov/ncidod/dhqp/hicpac_transcript-07-23.html).

“endorse the use of surgical masks for the routine care of patients with confirmed or suspected, novel influenza A (H1N1)”

“it is appropriate at this time to recommend the use of N95 or higher respiratory protection for procedures that are likely to generate small particle aerosols.” The procedures are then listed to include

“bronchoscopy, intubation under controlled or emergent situations, cardiopulmonary resuscitation, open airway suctioning and airway induction.”

Comment on Blachere et al: PCR positive is not the same as culture positive




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Institute of Medicine

1st September 2009

• HCWs (including non-hospital settings) in close contact with individuals with nH1N1 or ILIs should use fit-tested N95 respirators.

• Endorse current CDC guidelines.

Page 17 : “confirm the presence of airborne influenza virus in various clinic locations” Blachere et al (CID 2009 48 (4):438)

Also based on the Macinthyre study done in China

http://abcnews.go.com/Health/SwineFluNews/cdc-flu-mask-decision-based-flawed-study-authors/Story?id=8966585&page=1

But Macintyre group retracted their study

Large ongoing trial however conducted by John Hopkins which is yet to be published

(http://clinicaltrials.gov/ct2/show/NCT01249625).

Comparison of Non-clinical and Clinical Staff Infected by pH1N1

Non-clinical Clinical Statistical

significance (p) Total number of staff (n) 18759 40511

Number infected

A. During mandatory reporting for all staff

119 (0.63%) 249 (0.62%)

0.82 RR: 0.98 (95% CI 0.78-1.2)

B. Data during the entire pandemic period NA 1039 (2.6%)




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New Experimental Studies.

Experimental studies in which only PCR was used in diagnosis could not be considered conclusive because it would not be possible to ascertain whether such particles had viable virus that could result in transmission.

Must demonstrate both produc/on of infec/ous virus and inocula/on of live viruses on to pa/ents

Presence of viable viral aerosols in the exhaled breathe

1. Milton KD, Fabian P, Cowling JB. et al: Influenza virus aerosols in human exhaled breath: particle size, culturability and effect of surgical mask. PLOS Pathogen March 2013 Vol 9, Iss 3 e1003205

2. Fabian P, McDevitt, DeHaan HW. et al: Influenza virus in human exhaled breath: an observational study. PLOS ONE July 2008, Vol 3, Iss 7 e2691

There were at least two studies showing that viable virus may be transmitted to the host

1. Noti JD, Lindsley WG, Blachere FM. et al: Detection of influenza virus in cough aerosol generated in a simulated patient examination room. Clin Infect Dis 2012; 54 (1 June) 1569-1577

2. Bischoff EW, Reid T, Russell BG, Peters T: Transocular entry of seasonal influenza-attenuated virus aerosol and the efficacy of N95 respirators, surgical masks and eye protection in human. JID 2011:204 (15 July) 193-199

Sources were by artificially generated aerosols by simulators - difficult to be certain whether the situation was similar in real life.

Three-dimensional view of the aerosol exposure chamber.

Noti J D et al. Clin Infect Dis. 2012;54:1569-1577

Published by Oxford University Press on behalf of the Infectious Diseases Society of America 2012

Finally a study -‐ the sources were naturally infected influenza volunteers. Claims to be the first “end-‐point host-‐exposure and sampling study”

where special manikins were exposed to these volunteers.

Tang J, Gao CX, Cowling BJ, et al: Absence of detectable influenza RNA transmitted via aerosol during various human respiratory activities – experiments from Singapore and Hong kong. PLOS ONE September 2014 Vol 9, Iss 9 e107338 1-9

Methods The two studies had an identical aim, to test ….transmission of influenza from a naturally influenza-infected human to a life-like human manikin ‘recipient’ through real-life respiratory activities.

The HK study used a shop display manikin, customized for ‘mouth-‐inhaling’, to examine the quan/ty of influenza virus inhaled ….This study only examined the inhala/on phase of a poten/al recipient. The Singapore study used a commercial thermal, breathing manikin with a full breathing cycle to quan/fy the amount of influenza virus landing on facial skin sites.




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Finally a study -‐ the sources were naturally infected influenza volunteers. Claims to be the first “end-‐point host-‐exposure and sampling study”

where special manikins were exposed to these volunteers.

Tang J, Gao CX, Cowling BJ, et al: Absence of detectable influenza RNA transmitted via aerosol during various human respiratory activities – experiments from Singapore and Hong kong. PLOS ONE September 2014 Vol 9, Iss 9 e107338 1-9

Results

No influenza RNA was detected from any of these swabs with either team’s in-house diagnostic influenza assays.

Table 1. Results for the Hong Kong experiments (n = 9).

Tang JW, Gao CX, Cowling BJ, Koh GC, et al. (2014) Absence of Detectable Influenza RNA Transmitted via Aerosol during Various Human Respiratory Activities – Experiments from Singapore and Hong Kong. PLoS ONE 9(9): e107338. doi:10.1371/journal.pone.0107338 http://www.plosone.org/article/info:doi/10.1371/journal.pone.0107338

Table 2. Results for Singaporean experiments (n = 6).

Tang JW, Gao CX, Cowling BJ, Koh GC, et al. (2014) Absence of Detectable Influenza RNA Transmitted via Aerosol during Various Human Respiratory Activities – Experiments from Singapore and Hong Kong. PLoS ONE 9(9): e107338. doi:10.1371/journal.pone.0107338 http://www.plosone.org/article/info:doi/10.1371/journal.pone.0107338

“The outcomes of these two studies are presented together due to the similar and largely unexpected results”

Majority of droplets are from 10-‐100 µm.

N = Nicas et al (2005), D = Morawska (2006), Duguid (1946), L&R = Louden and Rpberts (1967)




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Factors affec1ng droplets evapora1on: ini/al size, composi/on, humidity, temperature velocity, exhala/on airflow, turbulence and ambience airflow.

pp 152

Factors affec/ng droplets evapora/on: ini/al size, composi/on, humidity, temperature, velocity, exhala/on airflow, turbulence and ambience airflow.

Can Influenza be transmi`ed by air? ……the risk is probably low

A. Are Most Respiratory Viral Infections Airborne?

Most studies done – Influenza and SARS




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Is SARS airborne? 2014 WHO ARI Guideline

Recommendations Ranking 1. Use clinical triage for early identification of patients with ARIs to prevent the transmission of ARI pathogens to

HCWs and other patients Strong

2. Respiratory hygiene (i.e. covering the mouth and nose during coughing or sneezing with a medical mask, tissue, or a sleeve or flexed elbow followed by hand hygiene) should be used in persons with ARIs to reduce the dispersal of respiratory secretions containing potentially infectious particles.

Strong

3. Spatial separation (distance of at least 1 metre) between beds should be maintained to reduce the transmission of ARI pathogens from one patient to another. Spatial separation (distance of at least 1 metre) between the patient and the HCW without the use of PPE should be maintained to reduce the transmission of ARI pathogens to the HCW

Strong

4. Cohorting, the placement of patients infected or colonized with the same pathogens in the same designated unit, zone or ward (with or without the same staff), or special measures, the placement of patients with the same suspected diagnosis (similar epidemiological and clinical information) in the same designated unit, zone or ward (with or without the same staff) within a health care setting, could be used in certain settings for the implementation of isolation precautions for patients with ARIs to reduce transmission of ARI pathogens to HCWs and other patients.

Conditional

5. According to the risk assessment (according to the procedure and suspected pathogen), PPE may be needed when providing care to patients presenting with ARI syndromes and may include an appropriate combination of the following: medical mask (surgical or procedure mask), gloves, long-sleeved gowns, and eye protection (goggles /face shields)

Strong

6. Personal protective equipment (PPE) including the use of gloves, long-sleeved gowns, eye protection (goggles or face shields) and facial mask (surgical/procedure mask or particulate respirators) should be used by HCWs during aerosol generating procedures that have been consistently associated with an increased risk of transmission of ARI pathogens1. The available evidence suggests performing or being exposed to endotracheal intubation either by itself or combined with other procedures (e.g. cardiopulmonary resuscitation, bronchoscopy) was consistently associated with increased risk of transmission.

Conditional

7. Adequately ventilated single rooms should be used when performing aerosol generating procedures that have been consistently associated with increased risk of ARI transmission.

Conditional

8. Vaccination for influenza should be used for HCWs caring for patients at higher risk of severe or complicated illness from influenza to reduce influenza illness & mortality among these patients

Strong

9. Considerations for Ultraviolet Germicidal Irradiation – no recommendations possible. - 10. Additional IPC precautions in health care settings for patients with ARIs should be based on the duration of

symptomatic illness (according to the pathogen and patient information1) to reduce the transmission of ARI pathogens to HCWs and other patients. Note that Standard Precautions should always be used. There is no evidence to support the routine application of laboratory tests for the determination of duration of IPC precautions.

Conditional

Ten WHO Recommendations for Infection control and Prevention of Acute Respiratory Viral Infections

Seto WH, Conly JM, et al: Infection prevention and control measures for acute respiratory infections in healthcare settings: an update. East Mediterr Health J. 2013;19 Suppl 1:S39-47. Review.

B. Can we define the aerosols genera/ng procedures?

Recommendations Overall Ranking

6. Personal protective equipment (PPE) including the use of gloves, long-sleeved gowns, eye protection (goggles or face shields) and facial mask (surgical/procedure mask or particulate respirators) should be used by HCWs during aerosol generating procedures that have been consistently associated with an increased risk of transmission of ARI pathogens1. The available evidence suggests performing or being exposed to endotracheal intubation either by itself or combined with other procedures (e.g. cardiopulmonary resuscitation, bronchoscopy) was consistently associated with increased risk of transmission.

Conditional




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One NIV and manual ventilation before intubation is the same study One study on NIV with OR > 1 One study on tracheostomy

3 studies all together

WHO meta-analysis

Poor infection control practices

HCW present during intubation is a factor but no factor related to NIV or manual ventilation




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NIVs OR>1

Tracheostomy

Aerosol-generating procedures Some procedures performed on patients are more likely to generate higher concentrations of respiratory aerosols than coughing, sneezing, talking, or breathing, presenting healthcare personnel with an increased risk of exposure to infectious agents present in the aerosol. Although there are limited objective data available on disease transmission related to such aerosols, many authorities view the following procedures as being very high exposure risk aerosol-generating procedures for which special precautions should be used: • Bronchoscopy • Sputum induction • Endotracheal intubation and extubation • Open suctioning of airways • Cardiopulmonary resuscitation • Autopsies

Both WHO/CDC: Intubation, bronchoscopy, autopsies, cardiopulmonary resuscitation, open suction of airways.

CDC only: extubation, sputum induction;

WHO only: collection of lower respiratory tract specimens.

Aerosol-generating high risk procedures.

About Sputum Induction Sputum induction is used to obtain sputum for diagnostic purposes when patients are unable to spontaneously expectorate a specimen. The procedure uses sterile water or hypertonic saline to irritate the airway, increase secretions, promote coughing, and produce a specimen. The CDC and OSHA both classify sputum induction as a high-risk procedure when performed on a person with suspected or known infectious TB




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Nebulizers

C. Is N95 Fit Tes/ng Necessary?

Is N95 Fit Testing Required?

• Most elements of the NIOSH respirator program (i.e., fit factor, protection estimates, etc.) are theoretical using mathematical models and have not been confirmed in practical work situations.

• In one NIOSH study, fit testing respirator assignment errors were as high as 20%.

From Bill Jarvis, CDC

Quantitative Fit Testing Does Not Ensure Health Care Worker Respiratory Protection

M Lee, S Takaya, R Long, M Joffe SHEA Abstract - Apr 2005

58 HCW never fit-tested 25/58 (43%) passed initial fit-test

– 19 passed with instruction = 76% total passes

3 months later, 49/58 re-tested – 47% recalled respirator type and passed fit-test – Passing at 3 months did not correlated with

passing at initial fit-test or receipt of instruction

No, fit testing is not needed. No added value to adequate training:

Hannum D, et al. The effect of respirator training on the ability of healthcare workers to pass a qualitative fit test. Infect Control Hosp Epidemiol 1996;17:636-40




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Seal check A method for determining

whether a respirator has been put on and adjusted to fit properly

Perform every time when a respirator is worn

Seal check

However, we disagree with the next sentence, which is inherently contradictory, “However, HCWs should undergo initial and periodic fit testing.” There is no sound evidence to support initial and periodic fit testing.

Infectious Diseases Society of America (IDSA) letter to CDC

February 4, 2005

D. Is nega/ve-‐pressure room an absolute necessity?

“The most important part of

tuberculosis infection control

is getting the patient into the

isolation room.”

Wurtz, 1996, ICHE




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Airborne transmission isolation room:

• Single room or cohorting • Negative pressure (2.5 Pa or .01 in water) • 6 - 12 air changes per hour - now it is > 12 • Exhaust air outside or recirculated HEPA filters

• Anteroom may enhance effects • Upper-room UVGI only as adjunct • Avoid within room circulation (eg. fans)

Graphs constructed by Wells-Riley equation to express the relationship between infection risk over ventilation rate, quanta generation rate and exposure time. (c) 5 minutes exposure time

(b) 10 minutes exposure time (a) 15 minutes exposure time

Journal of TB and Lung Diseases; Oct 2005

AR Escombe et al: Supervise by Imperial College and John Hopkins

65 rooms in 8 hospitals in Lima, Peru

Old Facilities: Median 37 ACH Modern Facilities: Median 18 ACH

Measurements in Grantham Chest Hospital Hong Kong (tests in 4 rooms) Windows open (100%), Doors open (100%) = 45.4 ACH Windows open (100%), doors close = 20.2 ACH Windows open (50%), doors close = 15.5 ACH

Windows close , doors close = 0.6 ACH Windows close, doors open = 3 .4 ACH




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http://www.who.int/water_sanitation_health/publications/natural_ventilation.pdf

What is natural ventilation?

TB incidence in Grantham and HA hospitals 1996-2005

HA hospitals: (257 cases) 60.4

GH: (5 cases) 65.2

Mean Incidence (per 100,000 pat year)

p = 0.9

Dr Seto,

I really enjoyed your insightful presentation yesterday... I am sorry you had to skip through so many of the slides in the interests of time.

I did my infectious disease training in Australia at Fairfield hospital... a stand-alone infectious diseases hospital that saw/treated most of the TB patients in Victoria-- we had single rooms, ]all of which opened up to a private balcony... we used lots of open air ventilation, high ACH and none of our staff converted their TSTs.

Marion A. Kainer MD, MPH, FRACP Medical Epidemiologist/ Infectious Diseases Physician Director, Hospital Infections and Antimicrobial Resistance Program Tennessee Dept. of Health




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Opening your windows,

The key to natural ventilation..

Microsoft Windows

I mean...to open your room windows!

Thank You

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